Desmoid tumors are fibrous tumors which usually occur in the tissue covering the intestines and may be provoked by surgery to remove the colon. The countless polyps in the colon predispose to the development of colon cancer; if the colon is not removed, the chance of colon cancer is considered to be very significant. Polyps may also grow in the stomach, duodenum, spleen, kidneys, liver, mesentery and small bowel. In a small number of cases, polyps have also appeared in the cerebellum. Cancers related to GS commonly appear in the thyroid, liver and kidneys. The number of polyps increases with age, and hundreds to thousands of polyps can develop in the colon.

It was first described in 1951.[4] At this time, there is no cure, and in its more advanced forms, it is considered a terminal diagnosis with a life expectancy of 35–45 years; treatments are surgery and palliative care, although some chemotherapy has been tried with limited success.[citation needed]

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Gardner syndrome is inherited in an autosomal dominant manner.[2] Typically, one parent has Gardner syndrome. Each of their children, male and female alike, are at 50% risk of inheriting the gene for Gardner syndrome. The risk increases in each succeeding generation, as affected occurs (cluster studies appear by registry).

Gardner syndrome is now known to be caused by mutation in the APC gene located in chromosome5q21 (band q21 on chromosome 5).[2] This is the same gene as is mutant in familial adenomatous polyposis (FAP), a more common disease that also predisposes to colon cancer. New genetic and molecular information has caused some genetic disorders to be split into multiple entities while other genetic disorders merge into one condition. After existing for most of the second half of the 20th century, Gardner syndrome has vanished as a separate entity. It has been merged into familial adenomatous polyposis (FAP) and is now considered simply a phenotypicvariant of FAP.

Gardner syndrome consists of adenomatous polyps of the gastrointestinal tract, desmoid tumours, osteomas, epidermoid cysts, lipomas, dental abnormalities and periampullary carcinomas. The incidence of the syndrome is 1:14,025 with an equal sex distribution. It is determined by the autosomal dominant familial polyposis coli gene (APC) on chromosome 5.[4]

Gardner syndrome can be identified based on oral findings, including multiple impacted and supernumerary teeth, multiple jaw osteomas which give a "cotton-wool" appearance to the jaws, as well as multiple odontomas, congenital hypertrophy of the retinal pigment epithelium (CHRPE), in addition to multiple adenomatous polyps of the colon. Gardner syndrome is also associated with FAP (Familial Adenomatous Polyposis) and may manifest as aggressive fibromatosis (desmoid tumors) of the retroperitoneum.[5]

Desmoid tumors arise most frequently from the aponeurosis of the rectus abdominal muscle of multiparous women. The extra-abdominal form is rare and desmoids of the breast may arise in the mammary gland or may occur as an extension of a lesion arising from the muscles of the chest wall. The incidence of mammary desmoid tumours is less than 0.2% of primary breast neoplasms. In Gardner’s syndrome the incidence ranges from 4% to 17%. Desmoid tumours associated with Gardner’s syndrome have been shown to have an alteration of the β-catenin pathway and over express β-catenin.[4]